ORIGINAL PAPERS

International Journal of Occupational Medicine and Environmental Health 2009;22(3):215 – 226 DOI 10.2478/v10001-009-0021-8 influence OF DIFFERENT KIND OF CLOTHING MATERIAL ON SELECTED CARDIOVASCULAR, RESPIRATORY AND PSYCHOMOTOR PARAMETERS DURING MODERATE PHYSICAL EXERCISE IZABELA CIESIELSKA1, MAREK MOKWIŃSKI2, and MONIKA ORŁOWSKA‑MAJDAK3 1 Technical University of Łódź Institute of Architecture of 2 Medical University of Łódź Department of Cell-to-Cell Communication, Chair of Experimental and Clinical Physiology 3 Medical University of Łódź Department of Experimental Physiology, Chair of Experimental and Clinical Physiology

Abstract Objectives: The aim of the experiment was to analyze the influence that the clothing material may have on human physiol- ogy and thermal comfort both at rest and physical effort to answer the question which fabric is better, a natural or a syn- thetic one. Materials and Methods: We measured some psychomotor parameters: critical flicker frequency (CFF), reaction time to auditory/visual stimuli (RT), concentration of attention (CA); cardiovascular parameters: blood pressure (BP), heart rate (HR) and respiratory parameters: tidal volume (VT), minute ventilation (VE), oxygen consumption (VO2), carbon dioxide output (VCO2), respiratory exchange ratio (RER) in human volunteers before, during and after physical effort. The subjects performed a 15-min treadmill test on treadmill wearing clothes made of two different materials: 100% coarse and 100% acrylic. An interview was conducted directly before the exercise test to assess the subjects’ general mood and wellbeing on that day. Besides, before and after the test, the subjects in their own words described the sensation they with respect to the physiological comfort of particular clothing. Results: The results showed that wearing clothes made of different fabrics had some influence on the cardiovascular and respiratory parameters during physical effort but it did not have any effect on the psychomotor skills. The perception of physiological comfort by the subjects wearing coarse wool or acrylic depended on their physiological state and differed at rest and after the physical effort. Conclusions: The course of physiological processes depends on the kind of clothing a given person is wearing. It is not possible to clearly define which of the two clothing materials: natural — wool, or synthetic — acrylic is better. Each of them exerts a different effect on the human organism. The usefulness of a given type of clothing material seems to depend on the human physiological state and the related thermoregulatory processes.

Key words: Physical Effort, Wool Set of Garment, Acrylic Set of Garment, Psychomotor Parameters, Cardiovascular Parameters, Respiratory Parameters

INTRODUCTION achieved in professional athletics, as well as on the ef-

The kind of clothing and the material it is made of may ficiency in non-sportive activities. There are also special determine the overall comfort of an individual wearing it standards for professional uniforms of firefighters, police- [1–4] and have impact on his/her everyday activities. The men, soldiers, and all people working under difficult ex- clothing material may also have influence on the results ternal conditions. Those standards concern the thermal,

Received: March 3, 2009. Accepted: June 9, 2009. Address reprint requests to M. Orłowska-Majdak, Department of Experimental Physiology, Chair of Experimental and Clinical Physiology, Medical University of Łódź, Mazowiecka 6/8, 92-215 Łódź, Poland (e-mail: [email protected]).

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physiological and ergonomic comfort of the users and the activity [12], reaction time [13], determination of the of the uniforms. The uniforms must comply with antioxidant activity of plasma and the level of immu- the European Norm with respect to the ergonomic com- noglobulin A [14] in humans wearing clothes made of fort, protection, fire resistance, thermal resistance, air per- different raw materials. meability, moisture evaporation, etc. [5]. The present study compares the influence of 100% coarse Most of the studies addressing this problem focus on the wool and 100% acrylic sets of clothing on selected psycho- improvement of structure and finishing technolo- motor, cardiovascular and respiratory parameters during gies. Non-durable and semi-durable flame retardants, submaximal physical effort. The following parameters based mostly on phosphate or phosphonate salts, continue were examined to evaluate the psychomotor skills: critical to be used in infrequently washed or disposable clothing. flicker frequency (CFF), reaction time to auditory/visual Recent improvements aim at imparting better wash resis- stimuli (RT) and concentration of attention (CA). We tance [6]. In some studies, extreme external working con- have decided to choose these parameters for the study as ditions are simulated in order to analyze the physiological in our opinion they are most susceptible to the changes comfort of wearing uniforms. Human trials are the com- evoked by physical effort. monly used methods to evaluate the physiological impact The CFF threshold is defined as the frequency at which of clothing on human physiology. Treadmill exercise test a flickering light cannot be distinguished from a steady, in a climatic chamber is usually performed to validate the non-flickering light. People can see lights flashing on and results obtained using small-scale test methods or mani- off for up to about 50 flashes per second (50 Hz). CFF is kins [3]. useful for assessing the temporal characteristics of the vi- The research concerning the effect that the clothing sual system and visual perception [15]. Additionally, CFF material may have on the physiological parameters thresholds correlate with various parameters of intelli- in humans was undertaken by a few research centers gence, and have been regarded by clinicians as a general worldwide. One study compared the influence of cloth- measure of the cortical processing capacity. For these rea- ing made of natural raw materials, like and , sons, CFF is used as a cognitive indicator in drug studies, with those made of synthetic materials like , as a measure of fatigue, and has been suggested as a diag- polyamide, and polypropylene [7]. It was generally fo- nostic measure for various brain diseases [16]. cused on the thermoregulation in humans wearing dif- RT is defined as “the interval between the onset of the ferent kinds of clothes. The use of clothing represents stimulus and the response under the condition that the an insulation layer and as such imposes a barrier against subject has been instructed to respond as rapidly as possi- heat transfer and evaporation from the skin surface. The ble” [17]. RT measurements have been employed in medi- influence of the kind of clothing material is especially cine and psychology and the measuring techniques have seen during the physical effort when increased muscu- been continuously improved [18]. lar activity results in increased heat production, affect- Attention is one of the components of consciousness [19]. ing the temperature balance in the body [7]. There are It was regarded as a principle of psychology by James literature reports supporting the effect of the clothing in 1890. Moskovitch, in 1979, defined attention as “a con- fabric on thermoregulation in exercising humans [8]. trol process that enables the individual to select from However, there are also reports in which no difference a number of alternatives the task he will perform or the was found in relation to the clothing material [9]. Very stimulus he will process and the cognitive strategy he will few studies concerned the measurements of skin tem- adopt to carry out these operations” [19]. Attention Defi- perature, body temperature, rectal temperature [10], cit Hyperactivity Disorder (ADHD) is presently one of the heart rate [11], systolic and diastolic blood pressure most frequently diagnosed disorders in children, and has

BP [1], oxygen consumption (VO2) [10], skeletal muscles’ recently been also recognized in adults [20].

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MATERIALS AND METHODS The treadmill was lifted to an altitude of 10 degrees to Twenty young healthy volunteers, students of the Medical the base. University of Łódź and the Technical University of Łódź The physical effort of the whole study group corresponded to 55–60% of the maximal volume of oxygen consump- (6 females and 14 males, aged 21–29 years), were eligible tion VO . for the study. The subjects had been informed about the 2max purpose of the project, the study design and procedures Physiological parameters and they signed consent to participate in the study. They Cardiovascular and respiratory parameters were asked to perform a 15-min treadmill exercise test Arterial blood pressure (BP) and heart rate (HR) were twice. At first, the subjects were wearing a 100% coarse measured before and after the treadmill exercise test us- wool clothing set. Then they changed into the clothes ing electronic sphygmomanometer OMRON M4-I. More- made of 100% acrylic. All the tests were performed at over, some respiratory parameters and HR were moni- room temperature of 17–23ºC (mean 19.8°C and 19.7°C tored during the test using VO2000 MedGraphics Cardio- for the stages of wearing woolen (I) and acrylic cloth- respiratory Diagnostic Systems that was compatible with ing (II), respectively) with relative humidity of 28–45% Breeze suite 6.2A MedGraphics software. The subject (mean 31.1% and 30.9% for stage I and II, respectively), examined was connected to the measuring system by the and atmospheric pressure of 977–1000 hPa (mean 989 hPa preVentTM mask attached to the pneumotach and umbili- and 989.9 hPa for stage I and II, respectively). Selected cal clip. Data regarding respiratory rate (RR/min), gas physiological parameters were measured before, during exchange coefficient (RER), carbon dioxide exhalation and after the physical exercise. The studies also comprised (VCO2 ml/min), oxygen inhalation (VO2 ml/min), tidal vol- an interview: each subject was to assess his/her general ume (VT BTPS ml), and minute ventilation (VE BTPS l/min) mood and wellbeing before the treadmill test, choosing were saved on PC. from a 15-item scale of response categories. Psychomotor skills Clothing description Critical flicker frequency (CFF) was measured using Both the sets of clothing tested during the study were de- the device constructed at the Nofer Institute of Occu- signed and made at the Institute of Architecture of Textiles, pational Medicine, Łódź, Poland. The subject examined Technical University of Łódź, Poland. Each set consisted was instructed to observe a flickering light. The flickering of a long-sleeved pullover and trousers. One set was made increased within the range of 20–60 Hz and the subject of 100% coarse-wool , and the other of 100% was asked to signal the moment at which he/she could not acrylic-knitted fabric. The wale density was 36-co­ distinguish the flickering light from a constant light. The lumnes/1 dm and the course stitch density 54 rows/1 dm digital indicator on the device showed the CFF threshold in both the fabrics. The air permeability for both sets was at which the subject did not recognize a single flash any similar and approximated 1500 dm3/m2×s. more. Reaction time (RT) was measured using the MRK-432 Exercise description device produced in Szczecin, Poland. This device gen- A 15-min exercise test was performed on the Track- erated light stimuli of red, green and white colour al- master treadmill with a programmed speed according ternately with low- and high-level sound stimuli. The to modified Bruce protocol. The speed was gradually subject was supposed to react to the red light with the increasing: from 3 km/h in the first minute of testing, right hand and to the low-level sound with the left hand through 4 km/h during the next 4 min and 5 km/h during as soon as possible. The total number of programmed another 5 min to 6 km/h during the last 5 min of testing. stimuli was 19.

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Concentration of attention (CA) was measured using Course of experiment cross apparatus K-6 produced in Szczecin, Poland. The The experiment started with an interview to assess the device had a front panel with arranged in 7 rows subjects’ general mood and wellbeing on the day of the and 7 columns of which the upper left and the top row testing. Then the subjects put on a 100% coarse wool were lamps. The program randomly switched on two set of clothing and became acclimatized to the room lamps at the same time, one in a column and one in temperature for 30 minutes. Meanwhile, they were ac- a row. The subject was supposed to press the appropriate quainted with the measuring devices and took part in which was at the intersection of the straight lines a few preliminary psychomotor tests. At the end of the between the two lamps. The measuring device counted acclimatization period, the subjects were asked to char- the number of correct responses per 49 light stimuli re- acterize the physiological comfort of the clothing worn leased. The speed of the popping lights was 50 changes during the test. Then, arterial blood pressure (SBP 1/ per min. DBP 1) and heart rate (HR 1) were measured using electronic sphygmomanometer OMRON M4-I. This Wellbeing questionnaire was followed by the CFF, RT and CA tests. Directly The questionnaire concerned the subject’s perception after that, the subject stepped on the treadmill, put on of his/her general mood and wellbeing before the physi- the facial mask for monitoring respiratory parameters, cal exercise, assessed on a 15-item scale of response cat- and fixed the HR detector on his/her chest. The sub- egories. It was based on the Positive and Negative Affect ject started walking on the treadmill at a programmed Scale (PANAS). The following response categories made speed that was gradually increased. The following pa- up the scale: rameters were monitored during the physical effort:

1. I feel very bad because I am very anxious. HR, RR, RER, VCO2, VO2, VT BTPS and VE BTPS. In 2. I feel very bad because I am strongly depressed. the first minute after the test, arterial blood pressure 3. I feel bad because I am anxious. (SBP 2/DBP 2) and heart rate (HR 2) were measured 4. I feel bad because I am depressed. and the psychomotor parameters (CFF, RT, and CA) 5. I feel rather bad. were assessed. After a 7.5-min interval, blood pressure 6. I feel rather bad because I am slightly anxious. (SBP 3/DBP 3) and heart rate (HR 3) were measured 7. I feel neutral, neither well nor bad. again, and the measuring procedure was repeated once 8. I feel quite well as I am slightly excited. more after another 2.5 min (10 min after termination 9. I feel quite well as I am quite satisfied. of treadmill test) for blood pressure (SBP 4/DBP 4) 10. I feel quite well as I generally have and heart rate (HR 4). that kind of mood. When the treadmill test was over, the subject described in 11. I feel well because I am in a good mood. his/her own words the sensation he/she had felt with re- 12. I feel well because I have a hope for a change spect to the physiological comfort of the coarse wool set for better. of clo­thing. 13. I feel well because I am positively excited. After this series of measurements, the subjects rested 14. I feel very well because I am relaxed. for at least 30 min, wearing their own clothes. Then they 15. I feel very well because I am fully satisfied. changed into the acrylic clothing set. The acclimatization The subjects responded to the questionnaire directly be- in the new clothing lasted 30 min. The whole measuring fore the treadmill test. Besides, before and after the test, procedure was repeated using the same time intervals be- the subjects were asked to describe in their own words the tween single measurements. The results concerning the physiological comfort of the two different kinds of cloth- resting state of the subjects were compared with those ob- ing they were wearing for the study. tained after the exercise test.

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Ethics RESULTS The study design was approved by the Biomedical Eth- Influence of clothing material ics Committee of the Medical University of Łódź, Po- on psychomotor parameters land, RNN/299/06/KB. The authors compared psychomotor parameters before and after the treadmill test in both the clothing sets. CFF Statistics was the only psychomotor parameter that has changed Statistical analysis was carried out using Statistica soft- significantly (p < 0.05), compared to the initial value, ware. The Shapiro-Wilk test confirmed the normality of while the subjects were wearing woolen clothes: it was data distribution. Student-t test was used for the depen- found to increase from 35.86±0.68 Hz to 37.19±0.66 Hz dent variables to check whether the testing results be- (Table 1). No statistically significant differences in CFF fore the physical effort differed significantly in relation values were noted during the stage when the subjects to the type of the clothing material tested. This test was had acrylic clothes on. We presume that the submaxi- also used to compare HR and respiratory parameters at mal physical effort may affect the visual perception of different time-points of the treadmill exercise test in the an individual but the level of changes may depend on subjects wearing the two clothing sets. Data obtained the kind of clothing he/she is wearing during the effort. from all the measurements performed during the tread- Moreover, we did not observe any statistically significant mill test were divided according to the four time inter- differences in CA and RT parameters in relation to the vals of the testing that corresponded to the increasing kind of clothing worn. intensity of physical effort. The first set of data referred to the measurements carried out within the 1st min Influence of clothing material on cardiovascular of testing, the second one after 5 min, the third one parameters before and after physical effort after 10 min and the fourth one after 15 min of the The values of SBP, DBP, and HR before and after the treadmill test. Respective data for the subjects wearing exercise test were compared in relation to the kind of coarse wool and acrylic clothing were compared. They clothing worn by the subjects (Table 2). It was found that were analyzed with the Shapiro-Wilk test which did not during the acclimatization period in each set of clothes, confirm the normality of their distribution. Mann-Whit- the BP and HR values differed significantly (p < 0.05). ney U test, ANOVA Friedman, and Schéffe test post Wearing the woolen clothes significantly increased the hoc were employed to compare respiratory parameters systolic BP (133.95±14.39 mmHg) compared to wear- and HR during the test in the subjects wearing the two ing the acrylic clothes (126.20±13.87 mmHg). In the clothing sets. The level of statistical significance for all group wearing woolen clothing, HR decreased sig- tests was p < 0.05. nificantly (81.45±11.20) as compared with respective

Table 1. Psychomotor parameters in subjects wearing 100% coarse wool and 100% acrylic clothing (mean±SE)

Coarse wool clothing Acrylic clothing Study parameter Before After Before After physical effort (B) physical effort (A) physical effort (B) physical effort (A) Critical flicker frequency (Hz) 35.86±0.68* 37.19±0.66* 36.93±0.71 37.91±0.71 Reaction time (ms) 343.40±8.24 341.81±8.23 340.30±11.30 341.59±10.49 Concentration of attention 38.30±1.80 38.65±1.90 38.70±1.60 38.25±1.81 (number of correct answers)

* Statistically significant difference as revealed by Student-t test for paired variables (A v. B). Other comparisons did not show anydifference in relation to the kind of clothing material.

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Table 2. Systolic (SBP) and diastolic (DBP) blood pressure and heart rate (HR) recorded before treadmill exercise test and at different time-points after the test in subjects wearing different sets of clothing (mean±SE)

Results Study parameter Coarse wool clothing (W) Acrylic clothing (A)

Before physical effort SBP1 133.95±3.21* 126.20±3.10* DBP1 81.95±1.69 77.60±2.19 HR1 81.45±2.50* 88.75±2.77* After physical effort (min) 1 SBP2 157.95±3.10* 148.15±3.22* DBP2 89.84±2.21 86.45±2.65 HR2 127.05±3.34 122.65±3.92 7.5 SBP3 135.70±3.28 131.78±2.81 DBP3 87.40±1.86 84.47±2.24 HR3 104.95±2.50 105.42±3.28 10 SBP4 130.94±3.45 126.05±2.03 DBP4 87.05±2.04 82.58±2.20 HR4 103.00±1.94 102.35±2.48 Level of significance as estimated by Student-t test SBP1 v. SBP2 P < 0.05 P < 0.05 for paired variables when comparing the results DBP1 v. DBP2 P < 0.05 P < 0.05 recorded before the exercise test and at different HR1 v. HR2 P < 0.05 P < 0.05 time-points after the effort. The lack of difference SBP1 v. SBP3 NS P < 0.05 is an evidence of the parameter’s regaining its DBP1 v. DBP3 P < 0.05 P < 0.05 inital value HR1 v. HR3 P < 0.05 P < 0.05 SBP1 v. SBP4 NS NS DBP1 v. DBP4 P < 0.05 P < 0.05 HR1 v. HR4 P < 0.05 P < 0.05

* Statistically significant difference as revealed by Student-t test for paired variables (A v. W). No other comparison showed any difference in relation to the kind of clothing material. NS — not significant.

values among subjects wearing acrylic (88.75±12.41). the treadmill test. As for the diastolic BP and HR, the The systolic BP in the subjects wearing woolen clothes values of these parameters after the effort remained (157.95±13.87 mmHg) was significantly higher than in higher than their initial levels, regardless of the type of the group wearing acrylic clothing (148.15±14.42 mmHg) clothing (p < 0.05). within the first minute after the treadmill test. Cardiovascular parameters recorded before the onset Influence of clothing material on respiratory of the experiment were compared with those collect- parameters and HR values during physical effort ed 1 min, 7.5 min, and 10 min after the physical effort The Mann-Whitney U test was employed to compare at both stages of the experiment. The aim of this com- the findings for respiratory parameters and HR during parison was to find out whether the kind of clothing may the four time intervals of the exercise test in the sub- have influence on the recovery time after the physical jects wearing both sets of clothing. It is worth noting effort (Table 2). Systolic BP regained its initial values that from 5th min to 15th min of testing, the RER co- earlier in the subjects wearing wool — within 7.5 min efficient reached higher values in the subjects wearing (SBP1 vs. SBP3, p = NS) than in those wearing acry­ wool than in those wearing acrylic (Fig. 1A). However, lic — within 10 min (SBP1 vs. SBP4, p = NS) after a statistically significant difference (p < 0.05) could be

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Table 3. Selected respiratory parameters during treadmill exercise test at the time intervals of 0–1st min, 2nd–5th min, 6th–10th min, and 11th–15th min in subjects wearing 100% coarse wool and 100% acrylic clothing (mean±SE)

Duration of physical RER VCO2 l/min VO2 l/min effort (min) W A W A W A 1 0.98±0.09 1.00±0.07 0.49±0.14 0.32±0.05 0.42±0.07 0.32±0.04 5 1.01±0.08* 0.84±0.02* 1.69±0.15* 1.35±0.11* 1.68±0.95 1.56±0.10 10 1.11±0.07* 1.00±0.01* 2.13±0.19 1.88±0.11 1.91±0.11 1.88±0.10 15 1.18±0.07 1.09±0.02 2.79±0.17 2.70±0.14 2.41±0.14 2.46±0.13

* Statistically significant difference (A v. W) as revealed by Mann-Whitney U test. It refers to the values recorded in subjects wearing 100% coarse wool clothes (W) compared to those wearing 100% acrylic clothes (A).

observed only after the 5th and 10th min of physical ef-

fort. The volume of CO2 exhalation (VCO2) was higher in the subjects dressed in woolen clothes after 5th, 10th, and 15th min of testing (Fig. 1B). However, the high- est statistically significant difference was noted after

the 5th min. The difference in minute O2 consumption in the subjects wearing both the types of clothes was not

significant (p > 0.05) (Fig. 1C). Moreover, the total O2 consumption during the testing in woolen and acrylic clothing was estimated based on curve plotting and the difference was not significant either (p > 0.05). The val-

ues of RER, VCO2 and VO2 are shown in Table 3.

All the other study parameters, namely RR, VTBTPS,

VEBTPS, and HR showed similar values at both the stages of the experiment at all the time intervals of the treadmill test. They are shown in Figs. 2A, B, C, and D. A large difference in RR values within the first minute of testing was noted between the subjects wearing wool (17.42±1.67) and acrylic (23.55±3.45). The difference is remarkable but was found to be of no statistical signifi- cance (Fig. 2A). The comparison of changes in selected respiratory param- eters and HR during the physical effort shows that these values were continuously increasing during the test both in the subjects wearing woolen and acrylic clothes. However, in those performing the test in acrylic clothes, RER de- *Statistically significant difference between the values for coarse wool creased after 5th min, to rapidly grow after the 15th min. and acrylic Also, the RR value in the subjects in acrylic clothes in- Fig. 1. Gas exchange parameters at 1st, 5th, 10th and 15th min creased significantly only towards the end of the pro- of treadmill exercise test in subjects wearing coarse wool or acrylic clothes: (A) respiratory coefficient (RER), (B) carbon grammed effort, which was approximately at the 15th min dioxide exhalation (VCO2), and (C) oxygen inhalation (VO2). of testing.

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Fig. 2. Respiratory parameters and heart rate at 1st, 5th, 10th and 15th min of treadmill exercise test in subjects wearing coarse wool

or acrylic clothes: (A) respiratory rate (RR), (B) tidal volume (VT), (C) minute ventilation (VE), and (D) heart rate (HR).

Table 4. Responses to questionnaire regarding the subjects’ general mood and wellbeing

Mood description Number of responses 1. I feel very bad because I am very anxious 0 2. I feel very bad because I am strongly depressed 0 3. I feel bad because I am anxious 0 4. I feel bad because I am depressed 0 5. I feel rather bad 0 6. I feel rather bad because I am slightly anxious 0 7. I feel neutral, neither well nor bad 6 8. I feel quite well as I am slightly excited 1 9. I feel quite well as I am quite satisfied 2 10. I feel quite well as I generally have that kind of mood 0 11. I feel well because I am in a good mood 8 12. I feel well because I have a hope for a change for better 0 13. I feel well because I am positively excited 0 14. I feel very well because I am relaxed 2 15. I feel very well because I am fully satisfied 1

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Assessment of the subjects’ wellbeing is overproduced due to anaerobic metabolism of glucose before the experiment resulting in lactic acid production. This may refer to our The present study involved an evaluation of the subjective experiment as the subjects have been recruited from perception of physiological comfort in relation to the type among students who are not used to exercise and usually of clothing worn during the treadmill test. Therefore, an lead a sedentary lifestyle. In the population who does not interview was conducted directly before the experiment to practice physical exercise regularly, the anaerobic thresh- assess the subjects’ general mood and wellbeing on that old (AT) occurs at a lower level than in sportsmen. In the particular day. This was done to eliminate the potential students at the University of Physical Education, the AT bias related to the effect that a negative attitude could level was reached at the point of a 60% maximum oxygen have had on the findings of the experiment. The interview consumption (VO2max) [21], and the first-minute changes in revealed that the subjects did not feel any major discom- lactic acid concentration in blood could be observed after fort that could have affected the evaluation. The findings the physical effort of intensity exceeding 40% VO2max [22]. of the interview are shown in Table 4. In our study, the intensity of physical effort was at the level

of 55–60% VO2max.

The fact that higher levels of RER and VCO2 could be DISCUSSION noted among subjects performing the test in 100% coarse Before the onset of the experiment, all the subjects shared wool clothing provides evidence that at the same level of an opinion that the coarse wool set of clothing was ex- physical effort, the human organism reacts in a different tremely unpleasant in contact with the skin, and they felt way depending on the type of the clothing material, and discomfort when wearing it. They reported an opposite the type of fibre in particular. The findings regarding RER sensation with respect to the acrylic set. However, their and VCO2 values indicate that performing exercise in 100% impression changed after the physical effort: they were coarse wool set of clothing seems to be a higher physical sweating and felt discomfort in the acrylic set of garments, effort to the system than does the performance in acrylic while felt comfortably in woolen clothes. This may have clothes. been due to the difference in the and structure The other respiratory parameters (RR, Vt, VE) also in- of the two materials. The textiles made of acrylic have creased during the exercise, but no statistically significant a lower air and liquid permeability than the woolen tex- differences depending on the type of fabric could be ob- tiles. This may be the reason for the differences in physi- served. A more remarkable increase in RR and VE values ological parameters observed during the physical effort during the exercise was found in the subjects wearing wool performed when wearing the two kind of clothing. (1.8× and 3.5×, respectively) than in those wearing acrylic The highest differences could be noted with respect to (1.4× and 2.9×, respectively). At the same time, it can be respiratory parameters, such as the mean value and dis- noted that the increase in the Vt value recorded during tribution of RER coefficient and the mean volume of physical exercise was more prevalent among the subjects exhaled CO2 (VCO2). The values of those parameters in- wearing woolen clothes, whereas in RR values among creased with the increasing level of physical effort and those wearing acrylic clothes. the time of testing in the subjects wearing both the sets The two parameters are controlled through slightly dif- of clothes. However, in the subjects wearing wool, RER ferent mechanisms. The results obtained by Flandrois and VCO2 were higher than in those wearing acrylic. The et al. [23] and Heistad et al. [24] suggest that the depth respiratory exchange ratio (RER) is known to increase of breathing is controlled by noradrenaline (NA), mostly during the physical exercise due to the hyperventila- through the stimulation of the adrenergic nervous system, tion and enhanced CO2 excretion. In the case of inten- whereas the rate of breathing by adrenaline (A), through sive effort, when the lactate threshold is exceeded, CO2 the activity of adrenal medulla. It is most likely that these

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two regulatory mechanisms (nervous and humoral) oper- be explained by the NA-A concept. In the persons wearing ate with a different intensity under particular conditions wool, the enhanced activity of the NA-ergic sympathetic of physical exercise that are due to the specific clothing system returns to normal values faster than that of the material of the outfit worn during the exercise. It seems hormonal-A system from adrenal medulla. Adrenaline re- that in the persons wearing 100% coarse wool clothing, tention in blood accounts for the higher values of HR that the effects of NA and the sympathetic system dominate, maintain for 10 min after the test. Unfortunately, blood whereas in those wearing 100% acrylic clothes, the effect concentrations of NA and A were not considered in this of adrenal medulla and A is more pronounced. study and thus there is no evidence that the NA‑A hypoth- The cardiovascular parameters (BP and HR) also differed esis is correct. significantly depending on the kind of clothing material. The comparison of the psychomotor parameters (RT BP values were higher among subjects wearing woolen and CA) before and after physical effort in the subjects clothes. A statistically significant difference was noted be- wearing different kind of clothing did not reveal any sig- fore the exercise test, at half an hour of acclimatization in nificant differences. Only the CFF value increased after specific clothing (SBP1), and then one minute after the test physical effort in the subjects wearing woolen set, but no (SBP2). The difference could be observed 7.5 and 10 min changes were observed among those wearing acrylic set, after the test (SBP3 and SBP4, respectively) but was no which suggests that the physical effort produced a favour- longer significant. The HR showed an opposite tenden- able change in this parameter only in the former group. It cy; it was higher after acclimatization in the acrylic set of is plausible that the physical exercise performed in acrylic clothes. The differences observed after the effort were clothes triggered a mechanism leading to decreased vas- varying and not significant. The comparison of A and NA cularization of the retina and worsened the conditions of effects on the cardiovascular system revealed that A con- its activity. This would stand in contrast to the generally tributed to higher HR, whereas NA increased the BP shared view that moderate-intensity exercise enhances the values [25]. Therefore, it can be concluded that in the activity of the central nervous system and exerts a positive subjects wearing woolen clothing, the NA-ergic nervous effect on the cognitive performance [13]. Thus, the posi- mechanism predominates over the humoral A mecha- tive change that referred to CFF in the subjects wearing nism, while in the subjects wearing 100% acrylic clothes, wool could have been expected in all the other psychomo- a reverse reaction can be observed. tor parameters under study. The effect of different clothing material on HR during It should be mentioned that the results of measurements physical effort has been investigated by Kwon et al. [26] in the subjects wearing acrylic clothes might be burdened who found higher HR values in individuals wearing syn- with an error due to the fact that this measurement was thetic (polyester) clothing than in those wearing cotton performed as the second one during the experiment. Al- clothing, as well as by Gavin et al. [10] who, however, did though the physical exercise that the subjects were to per- not observe any effect of the clothing fabric on HR in per- form did not involve maximal effort, some of the subjects, sons examined during physical effort. The findings of our although young and healthy, were tired as early as after study confirm that HR is intensified by wearing clothes the first trial. Thus, the physical effort performed in acrylic made of synthetic fabric. clothes (stage II of experiment) could have been more tir- The analysis of the cardiovascular parameters after physi- ing for them. In our study, we decided to apply a uniform cal effort and the rate of their returning to initial values re- experimental model having always the same kind of mate- vealed that in the subjects wearing woolen clothes, BP re- rial (wool) tested at stage I, after a preliminary series of gained its initial values faster (after 7.5 min) than in those experiments performed on two subjects which consisted in wearing acrylic clothes (after 10 min). HR remained higher changing the order of the materials tested. This series did for 10 min after the exercise test. These observations can not show any influence of the sequence of testing materials

224 IJOMEH 2009;22(3) INFLUENCE OF CLOTHING MATERIAL ON HUMAN PHYSIOLOGY ORIGINAL PAPERS on the study parameters. The woolen material was tested CONCLUSIONS first as we thought that wearing it might be less burden- 1. The kind of clothing material, or in other words, some for the thermoregulation process. We also expected whether the clothes are made of natural or man-made it would be a better starting point for the second stage of , has influence on some physiological param- the experiment performed in acrylic clothes. eters in humans during the performance of physical The effect of the clothing material on human physiologi- effort. These parameters include the respiratory and cal parameters is usually investigated in the context of the cardiovascular but not psychomotor parameters. thermal stress that may be associated with physical effort. 2. The wellbeing of individuals wearing acrylic clothes, In general, it is believed that the properties of clothing can in relation to the physiological comfort, is worse after considerably change the physiological conditions related the physical effort, in contrast to the sensation they to physical effort [7,27], but it has not always been possible have after wearing woolen clothing. to provide evidence that they affect the thermoregulatory 3. The changes in physiological parameters recorded mechanisms [10]. Zimniewska proved that even under during the physical effort in relation to the kind of static conditions, the temperature measured on the skin clothing material used in our experiment do not clear- surface depended on the kind of clothing and was higher ly demonstrate which type of material evokes lower or when the subjects worn polyester clothes than the linen higher load. ones [12,28]. 4. The type of material for the clothes to be worn during The most significant effect of clothing on the human body lies in that it hinders the transmission of excess heat with a physical effort should be selected depending on the water vapour from the skin surface, because clothing re- type, intensity and duration of the effort and taking into sists the passage of water vapour and thus decreases body account the potential effects on human physiology. heat loss by evaporative cooling. Moreover, clothing ab- sorbs liquid sweat by capillary action, taking sweat away ACKNOWLEDGEMENTS from the body surface, and reduces the cooling effect of evaporation. Natural fibres absorb sweat better than the The authors would like to thank Professor Dariusz Nowak man-made fibres. Therefore, the clothing made of natural for assistance in making arrangements for this research and fibres, which is capable of absorbing secreted sweat gradu- Dr. Marek Kasielski for inspiration in statistics. This work ally, is more comfortable during physical effort. was supported by the Medical University of Łódź, grant However, this refers to a short-term physical effort. no. 503-8079-1 and by the Polish State Committee for Scientific During a long-lasting effort, the absorption of sweat Research, grant no. 3T08E 051 27. increases the mass of the clothing worn, which in turn produces an additional load for an individual perform- REFERENCES ing exercise. Moreover, the evaporation process is hin- dered even more by wet clothing covering the body than 1. Hatch KL, Markee NK, Maibach HI. Skin response to fabric — by dry clothing. In view of the above, the thermoregula- a review of studies and assessment methods. Clothing Textiles tory processes may be more impeded in persons wearing Res J 1992;10(4):54–63. clothes made of natural fibers rather than synthetic ma- 2. Gwosdow AR, Stevens JC, Berlund LG, Stolwijk JA. Skin terials. Apart from that, the electrostatic field formed by Friction and Fabric Sensation in Neutral and Warm Environ- the charges accumulating on the surface of the synthetic ments. Textile Res J 1986;56(9):574–80. clothing material [28], but not on the natural material, 3. Rossi R. Interactions between protection and thermal comfort. has influence on the physiological parameters in the per- In: Scott RA, editor. Textile for protection. Cambridge: Wood- sons wearing synthetic clothing. head Publishing Limited; 2005. p. 233–60.

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